This invention relates to a method for selectively controlling the plating thickness on opposing sides of a body. More particularly, this invention relates to a method for simultaneously depositing metallic coatings on opposing sides of a substrate, the deposited coating being thinner on one side than the other.
It is often desirable to provide opposing sides of a substrate with a metal coating wherein the thickness of the coating is not equal on both sides. Various methods have been employed in the prior art in order to achieve this result. For example, one approach is an anode shielding method wherein a nonconductive shield is placed between the surface of the body upon which the thinner coating is desired and the anode. While theoretically this serves to increase the electrical resistance between the anode and the substrate, it has not been found to achieve the desired results in practice.
Accordingly, prior art researchers resorted to separate plating steps wherein each surface is masked while plating is carried out on the opposing surface. While providing the desired results, this approach requires two separate plating operations with additional steps of masking, etching, etc., required for each side.
Alternately, plating is carried out in one operation but the thicker of the desired coatings is applied to both sides. While this is usually not a detriment where inexpensive metals are plated, it is wasteful and uneconomical where expensive metals such as gold are employed.